Wakefulness level estimation apparatus

Abstract

A wakefulness level estimation apparatus includes: an estimation portion that estimates a level of wakefulness of a subject person based on one of a wakefulness level estimation function, of which a variable is a wakefulness level correlation value of the subject person, and a difference between the wakefulness level correlation value of the subject person and a reference value of the wakefulness level correlation value; a stimulation detection portion that detects whether an awakening stimulation is externally applied to the subject person; and a correction portion that, when the stimulation detection portion detects that the awakening stimulation is applied to the subject person, performs a correction of one of the reference value of the wakefulness level correlation value and the wakefulness level estimation function, which is used for estimating the level of wakefulness of the subject person.

What is claimed is: 
     
       1. A wakefulness level estimation apparatus, comprising: 
       an ECU having:
 an estimation portion operable to estimate a level of wakefulness of a subject person based on one of a wakefulness level estimation function, of which a variable is a wakefulness level correlation value of the subject person, and a difference between the wakefulness level correlation value of the subject person and a reference value of the wakefulness level correlation value; 
 a stimulation detection portion operable to detect whether an awakening stimulation is externally applied to the subject person and operable to detect that the stimulation is externally applied to the subject person when a vehicle runs in an area in which an awakening effect is produced by the stimulation being externally applied to the subject person, the area being one of (i) an area in which a facility is provided on a road to produce the awakening effect on the subject person, (ii) an area in which a tension stimulus is applied to the subject person due to a change of road circumstances and surrounding circumstances of the vehicle, and (iii) an area in which a physical stimulus that produces the awakening effect is applied to the subject person; and 
 a correction portion that, when the stimulation detection portion detects that the awakening stimulation is applied to the subject person, is operable to compare a level of wakefulness of the subject person estimated by the estimation portion after the simulation detection portion detects that the awakening stimulation is externally applied to the subject person with a level of wakefulness of the subject person estimated by the estimation portion before the stimulation detection portion detects that the awakening stimulation is externally applied to the subject person, and is operable to repeatedly perform a correction of one of the reference value of the wakefulness level correlation value and the wakefulness level estimation function, which is used for estimating the level of wakefulness of the subject person based on result of comparison of the level of wakefulness after the stimulation and the level of wakefulness before the stimulation, so as to make the level of wakefulness after the stimulation higher than the level of wakefulness before the stimulation. 
 
     
     
       2. The wakefulness level estimation apparatus according to  claim 1 , further comprising:
 an awakening actuation portion operable to apply the stimulation externally applied to the subject person; 
 wherein the stimulation externally applied to the subject person is provided by a plurality of stimuli including the tension stimulus; 
 the wakefulness level correlation value includes a plurality of blinking characteristic amounts including a number of blinks; and 
 when the stimulation detection portion detects that the subject person is externally stimulated by the tension stimulus, the correction portion performs the correction in a manner different from a manner when the subject person is stimulated by another stimulus than the tension stimulus. 
 
     
     
       3. The wakefulness level estimation apparatus according to  claim 2 , wherein when the stimulation detection portion detects that the subject person is stimulated by the tension stimulus, the correction portion performs the correction without changing a value pertaining to the number of blinks, which is one of the blinking characteristic amounts. 
     
     
       4. The wakefulness level estimation apparatus according to  claim 1 , wherein the level of wakefulness of the subject person is determined based on an eye-opening degree of the subject person. 
     
     
       5. The wakefulness level estimation apparatus according to  claim 1 , wherein when the stimulation detection portion detects that the stimulation is externally applied to the subject person, the correction portion corrects the wakefulness level estimation function when the level of wakefulness of the subject person estimated based on the wakefulness level estimation function does not reach a level of wakefulness at which it is determined that the subject person has been waken by the awakening stimulation. 
     
     
       6. The wakefulness level estimation apparatus according to  claim 1 , wherein the wakefulness level estimation apparatus is mounted on the vehicle, and the stimulation detection portion detects that the stimulation is externally applied to the subject person when the vehicle runs in an area that the awakening effect is produced by the stimulation externally applied to the subject person. 
     
     
       7. The awakening level estimation apparatus according to  claim 6 , wherein the area that the awakening effect is produced by the stimulation externally applied to the subject person is an area in which a facility is provided on a road to produce the awakening effect on the subject person. 
     
     
       8. The awakening level estimation apparatus according to  claim 6 , wherein the area that the awakening effect is produced by the stimulation externally applied to the subject person is an area in which the tension stimulus is applied to the subject person due to a change of road circumstances and surrounding circumstances of the vehicle. 
     
     
       9. The wakefulness level estimation apparatus according to  claim 8 , wherein:
 the wakefulness level correlation value includes a plurality of blinking characteristic amounts including a number of blinks; and 
 when the stimulation detection portion detects that the subject person is stimulated by the tension stimulus, the correction portion performs the correction without changing a value pertaining to the number of blinks, which is one of the blinking characteristic amounts. 
 
     
     
       10. The wakefulness level estimation apparatus according to  claim 6 , wherein the area that the awakening effect is produced by the stimulation externally applied to the subject person is an area in which a physical stimulus that produces the awakening effect is applied to the subject person. 
     
     
       11. The wakefulness level estimation apparatus according to  claim 1 , wherein the stimulation is a tension stimulus. 
     
     
       12. The wakefulness level estimation apparatus according to  claim 11 , wherein the tension stimulus increases the level of wakefulness of the subject person. 
     
     
       13. The wakefulness level estimation apparatus according to  claim 12 , wherein the tension stimulus is applied to a driver by at least one of a change of road circumstances, surrounding circumstances of the vehicle and a vehicle induced awakening actuation. 
     
     
       14. The wakefulness level estimation apparatus according to  claim 1 , wherein the correction portion performs the correction of one of the reference value of wakefulness level correlation value and the wakefulness level estimation function when a difference between:
 (a) the level of wakefulness estimated when the simulation detection portion detects that the awakening stimulation is externally applied to the subject person, and 
 (b) the level of wakefulness estimated before the simulation detection portion detects that the awakening stimulation, is externally applied to the subject person and is equal to or smaller than a first predetermined value. 
 
     
     
       15. The wakefulness level estimation apparatus according to  claim 1 , wherein the correction portion performs the correction of one of the reference value of wakefulness level correlation value and the wakefulness level estimation function when:
 (i) a difference between:
 (a) the level of wakefulness estimated when the simulation detection portion detects that the awakening stimulation is externally applied to the subject person, and 
 (b) the level of wakefulness estimated before the simulation detection portion detects that the awakening stimulation, is externally applied to the subject person and is equal to or smaller than a first predetermined value, 
 
 
       and
 (ii) the level of wakefulness estimated when the simulation detection portion detects that the awakening stimulation is externally applied to the subject person is larger than a second predetermined value which is larger than the first predetermined value. 
 
     
     
       16. The wakefulness level estimation apparatus according to  claim 1 , wherein the correction portion resets the level of wakefulness estimated when the simulation detection portion detects that the awakening stimulation is externally applied to the subject person by subtracting a certain value from the level of wakefulness, and repeatedly performs the correction of one of the reference value of wakefulness level correlation value and the wakefulness level estimation function so that the level of wakefulness becomes equal to the reset level of wakefulness.